1. Field of the Invention
The present invention relates to an LED driving circuit; and, more particularly, to an LED driving circuit capable of implementing constant current control of an LED channel by omitting a DC/DC converter and a control stage which have been necessarily applied for constant current control of an LED channel and by using a transformer having a plurality of primary windings connected to each other in series and a DC blocking capacitor.
2. Description of the Related Art
As the age of CRT (Cathode Ray Tube) which has occupied a monopolistic position until the 20th century draws to a close, a recent display industry is led by a FPD (Flat Panel Display) that is a new technology satisfying need of multimedia age such as high resolution and large screen.
Particularly, in the case of a large-display market, because an LCD (Liquid Crystal Digital) TV has rapidly grown, it is expected to play a leading role in terms of a future cost and marketability.
In the case of a conventional LCD TV, a CCFL (Cold Cathode Fluorescent Lamp) has been mainly used as a backlight light source, while a recent trend is to increasingly use an LED (Light Emitting Diode) having many advantages in terms of power consumption, lifetime, environment-friendly property, and so on.
In the case where the LED is used as the backlight light source of the LCD TV, each LED channel should be secured to be controlled with a constant current in order to secure uniform brightness over the entire screen.
In order to control each of the LED channels with the constant current, a current of the LED channel has been controlled with the constant current by applying a DC/DC converter such as a boost converter to each of the LED channels after acquiring an arbitrary DC voltage. This method has an advantage in that the current of each of the LED channels can be thoroughly controlled, but because the DC/DC converters and the control stages are required as many as the LED channels, a cost increases, power conversion efficiency is deteriorated due to the DC/DC converters, and the volume of an LED driving circuit increases. In addition, there is a problem of reducing reliability of a product due to an active device and ICs employed in the DC/DC converter.